The instant invention pertains to an inkjet ink composition. More particularly, the invention pertains to an inkjet ink comprising a soluble colorant and a vehicle, wherein the vehicle is comprised of an aqueous continuous phase and a “microemulsified” oil phase.
Inkjet printing is a non-impact printing process in which droplets of ink are deposited on print media, such as paper, to form the desired image. The droplets are ejected from a printhead in response to electrical signals generated by a microprocessor. Inks used in such recording are subject to rigorous demands including, for example, good dispersion stability, ejection stability, and good fixation to media.
Both dyes and pigments have been used as colorants for inkjet inks. Pigments can provide excellent durability with regard to fade resistance (light fastness) and good chroma when formulated properly. Dyes provide good chroma and are considered easier to formulate, but are less lightfast.
Dye-based inks may suffer from other deficiencies, for example, images printed with dye inks tend to lack water fastness, and suffer from bleed and feathering. Solutions to these problems often cause other problems, for example, applying a fixer to increase water fastness tends to reduce chroma.
The background of U.S. Pat. No. 6,261,350 provides a good discussion of dye ink formulation and problems. Art related to improved dye formulations includes the following references.
U.S. Pat. No. 4,783,220 pertains to ink comprising oil-soluble dye in association with surfactant vesicles. Disclosed is an oil-soluble dye associated with (cationic) dioctadecyldimethyl ammonium bromide vesicles.
U.S. Pat. No. 5,116,409 pertains to aqueous inks comprising water-soluble anionic dyes and certain surfactants. Disclosed is an aqueous ink with an anionic dye and cetyl trimethylammonium bromide (CTAB) as surfactant.
U.S. Pat. No. 5,565,022 pertains to an aqueous ink comprising water, dye, oil and an amphiphile to solublized the oil. Disclosed is a composition comprising water, an anionic water soluble dye, ethylene glycol phenyl ether (oil) and sodium xylene sulfonate amphihile.
All of the disclosures of the above-identified publications are incorporated by reference herein for all purposes as if fully set forth.
There is still a need for increased chroma and improved edge acuity and water fastness in dye-based inkjet inks.